/*
 * Copyright (C) 2009 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.collect;

import static java.util.Objects.requireNonNull;

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.ImmutableMap.IteratorBasedImmutableMap;
import com.google.errorprone.annotations.Immutable;
import com.google.j2objc.annotations.WeakOuter;

import java.util.Map;
import javax.annotation.CheckForNull;

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@code RegularImmutableTable} optimized for dense data.
 */
@GwtCompatible
@Immutable(containerOf = {"R", "C", "V"})
@ElementTypesAreNonnullByDefault
final class DenseImmutableTable<R, C, V> extends RegularImmutableTable<R, C, V>
{
    private final ImmutableMap<R, Integer> rowKeyToIndex;
    private final ImmutableMap<C, Integer> columnKeyToIndex;
    private final ImmutableMap<R, ImmutableMap<C, V>> rowMap;
    private final ImmutableMap<C, ImmutableMap<R, V>> columnMap;

    @SuppressWarnings("Immutable") // We don't modify this after construction.
    private final int[] rowCounts;

    @SuppressWarnings("Immutable") // We don't modify this after construction.
    private final int[] columnCounts;

    @SuppressWarnings("Immutable") // We don't modify this after construction.
    private final @Nullable
    V[][] values;

    // For each cell in iteration order, the index of that cell's row key in the row key list.
    @SuppressWarnings("Immutable") // We don't modify this after construction.
    private final int[] cellRowIndices;

    // For each cell in iteration order, the index of that cell's column key in the column key list.
    @SuppressWarnings("Immutable") // We don't modify this after construction.
    private final int[] cellColumnIndices;

    DenseImmutableTable(
            ImmutableList<Cell<R, C, V>> cellList,
            ImmutableSet<R> rowSpace,
            ImmutableSet<C> columnSpace)
    {
        @SuppressWarnings("unchecked")
        @Nullable
        V[][] array = (@Nullable V[][]) new Object[rowSpace.size()][columnSpace.size()];
        this.values = array;
        this.rowKeyToIndex = Maps.indexMap(rowSpace);
        this.columnKeyToIndex = Maps.indexMap(columnSpace);
        rowCounts = new int[rowKeyToIndex.size()];
        columnCounts = new int[columnKeyToIndex.size()];
        int[] cellRowIndices = new int[cellList.size()];
        int[] cellColumnIndices = new int[cellList.size()];
        for (int i = 0; i < cellList.size(); i++)
        {
            Cell<R, C, V> cell = cellList.get(i);
            R rowKey = cell.getRowKey();
            C columnKey = cell.getColumnKey();
            // The requireNonNull calls are safe because we construct the indexes with indexMap.
            int rowIndex = requireNonNull(rowKeyToIndex.get(rowKey));
            int columnIndex = requireNonNull(columnKeyToIndex.get(columnKey));
            V existingValue = values[rowIndex][columnIndex];
            checkNoDuplicate(rowKey, columnKey, existingValue, cell.getValue());
            values[rowIndex][columnIndex] = cell.getValue();
            rowCounts[rowIndex]++;
            columnCounts[columnIndex]++;
            cellRowIndices[i] = rowIndex;
            cellColumnIndices[i] = columnIndex;
        }
        this.cellRowIndices = cellRowIndices;
        this.cellColumnIndices = cellColumnIndices;
        this.rowMap = new RowMap();
        this.columnMap = new ColumnMap();
    }

    /**
     * An immutable map implementation backed by an indexed nullable array.
     */
    private abstract static class ImmutableArrayMap<K, V> extends IteratorBasedImmutableMap<K, V>
    {
        private final int size;

        ImmutableArrayMap(int size)
        {
            this.size = size;
        }

        abstract ImmutableMap<K, Integer> keyToIndex();

        // True if getValue never returns null.
        private boolean isFull()
        {
            return size == keyToIndex().size();
        }

        K getKey(int index)
        {
            return keyToIndex().keySet().asList().get(index);
        }

        @CheckForNull
        abstract V getValue(int keyIndex);

        @Override
        ImmutableSet<K> createKeySet()
        {
            return isFull() ? keyToIndex().keySet() : super.createKeySet();
        }

        @Override
        public int size()
        {
            return size;
        }

        @Override
        @CheckForNull
        public V get(@CheckForNull Object key)
        {
            Integer keyIndex = keyToIndex().get(key);
            return (keyIndex == null) ? null : getValue(keyIndex);
        }

        @Override
        UnmodifiableIterator<Entry<K, V>> entryIterator()
        {
            return new AbstractIterator<Entry<K, V>>()
            {
                private int index = -1;
                private final int maxIndex = keyToIndex().size();

                @Override
                @CheckForNull
                protected Entry<K, V> computeNext()
                {
                    for (index++; index < maxIndex; index++)
                    {
                        V value = getValue(index);
                        if (value != null)
                        {
                            return Maps.immutableEntry(getKey(index), value);
                        }
                    }
                    return endOfData();
                }
            };
        }
    }

    private final class Row extends ImmutableArrayMap<C, V>
    {
        private final int rowIndex;

        Row(int rowIndex)
        {
            super(rowCounts[rowIndex]);
            this.rowIndex = rowIndex;
        }

        @Override
        ImmutableMap<C, Integer> keyToIndex()
        {
            return columnKeyToIndex;
        }

        @Override
        @CheckForNull
        V getValue(int keyIndex)
        {
            return values[rowIndex][keyIndex];
        }

        @Override
        boolean isPartialView()
        {
            return true;
        }
    }

    private final class Column extends ImmutableArrayMap<R, V>
    {
        private final int columnIndex;

        Column(int columnIndex)
        {
            super(columnCounts[columnIndex]);
            this.columnIndex = columnIndex;
        }

        @Override
        ImmutableMap<R, Integer> keyToIndex()
        {
            return rowKeyToIndex;
        }

        @Override
        @CheckForNull
        V getValue(int keyIndex)
        {
            return values[keyIndex][columnIndex];
        }

        @Override
        boolean isPartialView()
        {
            return true;
        }
    }

    @WeakOuter
    private final class RowMap extends ImmutableArrayMap<R, ImmutableMap<C, V>>
    {
        private RowMap()
        {
            super(rowCounts.length);
        }

        @Override
        ImmutableMap<R, Integer> keyToIndex()
        {
            return rowKeyToIndex;
        }

        @Override
        ImmutableMap<C, V> getValue(int keyIndex)
        {
            return new Row(keyIndex);
        }

        @Override
        boolean isPartialView()
        {
            return false;
        }
    }

    @WeakOuter
    private final class ColumnMap extends ImmutableArrayMap<C, ImmutableMap<R, V>>
    {
        private ColumnMap()
        {
            super(columnCounts.length);
        }

        @Override
        ImmutableMap<C, Integer> keyToIndex()
        {
            return columnKeyToIndex;
        }

        @Override
        ImmutableMap<R, V> getValue(int keyIndex)
        {
            return new Column(keyIndex);
        }

        @Override
        boolean isPartialView()
        {
            return false;
        }
    }

    @Override
    public ImmutableMap<C, Map<R, V>> columnMap()
    {
        // Casts without copying.
        ImmutableMap<C, ImmutableMap<R, V>> columnMap = this.columnMap;
        return ImmutableMap.<C, Map<R, V>>copyOf(columnMap);
    }

    @Override
    public ImmutableMap<R, Map<C, V>> rowMap()
    {
        // Casts without copying.
        ImmutableMap<R, ImmutableMap<C, V>> rowMap = this.rowMap;
        return ImmutableMap.<R, Map<C, V>>copyOf(rowMap);
    }

    @Override
    @CheckForNull
    public V get(@CheckForNull Object rowKey, @CheckForNull Object columnKey)
    {
        Integer rowIndex = rowKeyToIndex.get(rowKey);
        Integer columnIndex = columnKeyToIndex.get(columnKey);
        return ((rowIndex == null) || (columnIndex == null)) ? null : values[rowIndex][columnIndex];
    }

    @Override
    public int size()
    {
        return cellRowIndices.length;
    }

    @Override
    Cell<R, C, V> getCell(int index)
    {
        int rowIndex = cellRowIndices[index];
        int columnIndex = cellColumnIndices[index];
        R rowKey = rowKeySet().asList().get(rowIndex);
        C columnKey = columnKeySet().asList().get(columnIndex);
        // requireNonNull is safe because we use indexes that were populated by the constructor.
        V value = requireNonNull(values[rowIndex][columnIndex]);
        return cellOf(rowKey, columnKey, value);
    }

    @Override
    V getValue(int index)
    {
        // requireNonNull is safe because we use indexes that were populated by the constructor.
        return requireNonNull(values[cellRowIndices[index]][cellColumnIndices[index]]);
    }

    @Override
    SerializedForm createSerializedForm()
    {
        return SerializedForm.create(this, cellRowIndices, cellColumnIndices);
    }
}
